The easy explanation is by what you achieve compared to what you wished to achieve.

As a writer, the best judge is usually sales of books. This would indicate people like your work, free reads are a slight comparison, but are they? A person has not committed to buying a book, I can tell you categorically free reads do not (!) lead to sales.

Do you count the number of friends who tell you they think your work is good?

This is a good indicator some people like your work, in my case, it would appear to be the only readers I have kept.

The most damned are those who lie to you, the old, "I'll buy your book" ploy. I forgot how many times I read that in the last six months and surprise-they lied.